1. Field of the Invention
The present invention relates to a composite magnetic head, a composite therefor, and a method of manufacturing such a composite magnetic head and a composite therefor, and more particularly to a composite magnetic head for use in a magnetic disk drive, a composite therefor, and method of manufacturing such a composite magnetic head and a composite therefor.
2. Description of the Related Art
It has been proposed to fabricate a magnetic head trailing core of a composite material comprising Mn--Zn ferrite and ceramics whose principal component is CaTiO.sub.3 in order to reduce the inductance of the trailing core to render the magnetic head suitable for higher frequencies. FIG. 1 of the accompanying drawings is a perspective view of a composite magnetic head made of such a composite material. FIG. 2 of the accompanying drawings illustrates in perspective a core chip used in the composite magnetic head shown in FIG. 1.
As shown in FIG. 1, the composite magnetic head, generally denoted as 2, has a structure comprising integrally a slider body 4 having air bearings, and a core chip 6 serving as a recording/reproducing section for writing desired information on and reading desired information from a magnetic disk.
Specifically, the slider body 4 has air bearings 8, 10 on its upper surface which include leading ramps 12 respectively on their rear ends and trailing chamfers 14 respectively on their front ends. The slider body 4 also has a coil winding groove 16 defined in a front end thereof for housing a coil therein, and a core chip insertion groove 18 defined in a front end portion thereof and extending from the upper surface of the air bearing 8 to the lower surface of the slider body 4. The core chip 6 is inserted in the core chip insertion groove 18 and fixed in place by a glass body 20. The slider body 4 may be made of nonmagnetic ceramics of CaTiO.sub.3 to prevent the recording/reproducing efficiency of the core from being lowered due to flux leakage.
As shown in FIG. 2, the core chip 6 comprises a trailing core 22 and a leading core 24. The leading core 24 has a C-shaped cross section and a coil winding groove 26 defined therein. The trailing core 22 has an I-shaped cross section with no coil winding groove. The C-shaped leading core 24 has upper and lower arms spaced from each other. The upper arm has a distal end cut off to define a magnetic gap 28 of a certain depth. The distal ends of the upper and lower arms of the leading core 24, and a side surface of the trailing core 22 are joined to each other through a gap glass layer 30, with the magnetic gap 28 defined therebetween. A space defined below the magnetic gap 28 between the leading core 24 and the trailing core 22 is filled up with an apex glass 32. The leading core 24 is made of Mn--Zn ferrite.
The trailing core 22 is made of a composite having a Mn--Zn ferrite segment 34, a CaTiO.sub.3 segment 36, and a glass layer 38 which joins the segments 34, 36 to each other.
The trailing and leading cores 22, 24 jointly have a track forming region 40 defined as a vertical step in upper ends thereof, providing a track 42 of a predetermined width on one side of the upper ends of the trailing and leading cores 22, 24. The track 42 has a trailing chamfer 44 on the upper surface of a front end thereof and a leading chamfer 46 on the upper surface of a rear end thereof. The track 42 has an upper surface 48 positioned on the trailing core 22, and an upper surface 50 positioned on the leading core 24, the upper surfaces 48, 50 being slidable surfaces on which a magnetic disk slides.
There has been proposed a monolithic magnetic head as shown in FIG. 3 of the accompanying drawings, which includes a trailing core made of a composite comprising Mn--Zn ferrite and ceramics whose principal component is CaTiO.sub.3 in order to reduce the inductance of the trailing core to render the magnetic head suitable for higher frequencies.
As shown in FIG. 3, the monolithic magnetic head, generally denoted at 52, has the trailing core 22 fixed to the front end of a leading core 24, which has air bearings 54, 56, 58.
Each of the air bearings 54, 56, 58 has a leading ramp 60 on its rear end. The leading core 24 has a central portion on which the air bearing 58 is disposed, the central portion having a front end 62 of a C-shaped cross section with a coil winding groove 26 defined therein. The trailing core 22, which is mounted on the front end 62, has an I-shaped cross section with no coil winding groove. An upper portion of the front end 62 is cut off to define a magnetic gap 28 of a certain depth. The distal ends of the upper and lower arms of the front end 62 of the leading core 24, and a side surface of the trailing core 22 are joined to each other through a gap glass layer 30, with the magnetic gap 28 being defined therebetween. A space defined below the magnetic gap 28 between the front end 62 of the leading core 24 and the trailing core 22 is filled up with an apex glass 32. The leading core 24 is made of Mn--Zn ferrite.
The trailing core 22 has a trailing chamfer 44 on the upper surface of a front end thereof. The trailing core 22 has an upper surface 48 and the air bearing 58 has an upper surface 50, with a track forming surface 64 defined on both side surfaces across the upper surfaces 48, 50. The upper surfaces 48, 50 are slidable surfaces on which a magnetic disk slides.
In each of the composite magnetic head 2 and the monolithic magnetic head 52, the trailing core 22 is made of a composite having a Mn--Zn ferrite segment 34, a CaTiO.sub.3 segment 36, and a glass layer 38 which joins the segments 34, 36 to each other.
Therefore, the Mn--Zn ferrite segment 34 has a small thickness to reduce the inductance of the magnetic head core to render the magnetic head suitable for higher frequencies. Since the nonmagnetic CaTiO.sub.3 segment 36 is joined to the Mn--Zn ferrite segment 34, the overall thickness of the trailing core 22 is kept large to maintain a desired mechanical strength even if though the Mn--Zn ferrite segment 34 is relatively thin.
However, since a boundary layer between the Mn--Zn ferrite segment 34 and the CaTiO.sub.3 segment 36 is exposed on the sliding surface 48 and lies perpendicularly to the sliding surface 48, signals recorded on the magnetic disk are read by an edge 66 of the Mn--Zn ferrite segment 34 near the boundary layer, as well as by the magnetic gap 28, resulting in a readout error.
To eliminate such a readout error, it may be possible to extend the trailing chamfer 44 toward the Mn--Zn ferrite segment 34 to make the edge 66 blunt. However, the Mn--Zn ferrite segment 34 is so thin that the magnetic gap 28 tends to be broken when the trailing core 22 is chamfered to produce the trailing chamfer 44 that extends to the Mn--Zn ferrite segment 34.
If the slider body 4 shown in FIG. 1 is made of CaTiO.sub.3, then since CaTiO.sub.3 has a large coefficient of friction against the magnetic disk surface, the slider body 4 and/or the magnetic disk is liable to be damaged when the slider body 4 slidingly contacts the magnetic disk surface. One solution has been to coat a nonmagnetic ceramics plate with glass by sputtering or the like, holding an Mn--Zn ferrite plate against the glass-coated nonmagnetic ceramics plate, and pressing them against each other with heat, for thereby making at least a disk sliding portion of the slider body, of Mn--Zn ferrite (see Japanese laid-open patent publication No. 3-273520).
The glass coated by sputtering or the like forms a very thin film, and hence fails to bear a thermal stress developed when the Mn--Zn ferrite segment and the nonmagnetic ceramics segment are joined, due to the difference between their coefficients of thermal expansion. Consequently, the composite made of Mn--Zn ferrite and the nonmagnetic ceramics tends to be curved or cracked.